After one no show -I will not allow them to schedule online ( they must call) if there is two- ( I never had this,but would explain policy and charge them percent of appt. if they miss- so hold time and appt with a card and or send bill in mail. If habitual " no show" then they should understand to pay in advance or hold with card- hopefully they respect your time and if they have a problem then let them no show elsewhere!